Hoofnagle co-authored “Behavioral Advertising: The Offer You Cannot Refuse” with four technical researchers: Ashkan Soltani, Nathan Good, Dietrich James Wambach, and Mika Ayenson. They developed custom tools and software to document web-tracking mechanisms, which revealed how advertisers use obscure technologies to monitor Internet activity—making online tracking virtually impossible to avoid.

The annual CPDP award honors the best paper written by an interdisciplinary team of researchers that advances new ideas in privacy and data protection. Behavioral Advertising was selected by a jury of prominent European academics and representatives from the U.S. and Asia.

“Advertisers are so invested in the idea of a personalized Web that they do not think consumers are competent to decide to reject it,” the team wrote. “We argue that policymakers should fully appreciate the idea that consumer privacy interventions can enable choice, while the alternative pure marketplace approaches can deny consumers opportunities to exercise autonomy.”

The award-winning paper is part of research Hoofnagle began years ago with Soltani, then a UC Berkeley School of Information graduate student, and continues today with Good, who earned his Ph.D. there in 2007.

Tracking the trackers

In 2009, a team of graduate researchers under Hoofnagle’s supervision published a report documenting how advertisers were using persistent tracking technologies that were mostly unknown to consumers. The report made major headlines, and was cited by Congress and by the Federal Trade Commission.

Two years later, Hoofnagle focused on new ways in which online users were being monitored. His research team was the first to elucidate the extent to which advertisers used “Flash” technology both to track individuals and to prevent them from blocking tracking.

“In this most recent paper, we document a shift away from Flash to HTML5, which as a technology has more ability to track users than standard cookies,” Hoofnagle explained. “Building upon our previous work, we show that it’s practically impossible for privacy-concerned users to avoid tracking. This has implications for both theory and the practice of consumer protection online.”

Hoofnagle said the most gratifying part of the CPDP award is that his paper was built on research conducted by undergraduates through a National Science Foundation grant. The grant facilitates a summer initiative, led by Hoofnagle and College of Engineering Dean Shankar Sastry, which provides graduate school-level mentorship for roughly a dozen students from colleges without research programs.

“They’re responsible for reading the entire literature of the field, choosing novel issues to investigate, and executing an experiment—all in about nine weeks,” Hoofnagle said. “What I learned is that when you give young people real responsibility and tell them that the project succeeds or fails based upon their input, they’ll rise to the occasion.”

Hoofnagle also credits UC Berkeley’s Data Science Initiative for training new students in programming languages and quickly bringing them up to speed for research.

“Good educational experiences are expensive and labor intensive,” he said. “Most students nowadays never get individual instruction. We can’t lose sight of the effectiveness of experiences similar to the tutorial system. If we want fully developed and resilient students, we have to invest in in-person supervision.”